Hydraulic pressure control apparatus

ABSTRACT

A stamping apparatus includes a pressure pad means for supporting a blank and a movable upper die portion for shaping the blank. Hydraulic cushion means yieldably opposes movement of the pressure pad means during shaping of the blank in response to movement of the upper die through a work stroke. At a predetermined point in the work stroke, an expansion chamber, connected by passageways to the hydraulic cushion means, expands at a rate sufficient to release the hydraulic pressure in the hydraulic cushion means such that the yieldable opposition of the hydraulic cushion means is removed.

D United States Patent [151 3,636,749

Heiser Jam. 25, 1972 [54] HYDRAULIC PRESSURE CONTROL 3,202,411 8/1965Heiser 72/351 A US 3,267,715 8/1966 W1ll1amson.....

3,435,653 4/1969 Scaletta et a1. [72] Inventor; Elmer Heiser 3313 p OakLane p 3,453,848 7/1969 Williamson ..72/351 ma, Ohio 44130 PrimaryExaminerRichard J. l-lerbst Flled! y 20, 1969 AttorneyYount & Tarolli 21A l. N 826 120 l 1 pp 0 57 ABSTRACT 52 us. Cl ..72 3s1 A P *P includes aP" P means for P- [511 InLCl t l 26/14 porting a blank and a movableupper die portion for shaping 58 Field of Search ..267/1l A 64 A- 72/351the blank- Hydraulic cushion means Yieldably PP movement of the pressurepad means during shaping of the blank in 56] References Cited responseto movement of the upper die through a work stroke. At a predeterminedpoint in the work stroke, an expansion UNITED STATES PATENTS chamber,connected by passageways to the hydraulic cushion means, expands at arate sufficient to release the hydraulic 1,926,012 9/1933 Ferr s..72/351 pressure in the hydraulic cushion means Such that the yie|da yg ble opposition of the hydraulic cushion means is removed. an cwer3,085,530 4/1963 Williamson ..72/351 22 Claims, 14 Drawing FiguresPATENIEU m2 51am SHEET 1 BF 5 SON/v FIG! I NVEN TOR. EL MER F He/swWEWEB M25 :92 3,636,749,

sum 3 or 5 F165 FIG .6

INVENTOIL ELMER E HE/SEl? PATENTED JAMS 1972 SHEEF Q U? 5 HYDRAULICPRESSURE CONTROL APPARATUS The present invention relates to a stampingapparatus. including a hydraulic cushion for yieldably biasing apressure pad against a member while the latter moves through a workstroke and in which the pressure in the cushion is released after themember has moved through a predetermined part of the work stroke.

A stamping apparatus to draw sheet material from its flat blank shapeinto a shell commonly involves the use of a pressure pad. The pressurepad is used to hold the flow of the material against the die as theblank is drawn to form the shell.

If the yieldable opposing force on the pressure pad is not great enough,or the force is prematurely removed, the peripheral material of theblank will not flow into a smooth shell, but will wrinkle and may besubsequently torn in the shaping process. On the other hand, whenexcessive force is applied to the pressure pad or the force is notremoved after the shell is partially formed, the shell wall section maybe substantially changed during shaping of the shell and in additionwhiskering and tearing of the peripheral material may occur.

Pressure control is particularly important in the closure industry wherethe material used for caps or covers is prefinished. One surface iscoated with a plastic coating which becomes the inside of the cap andthe other surface is printed with the necessary lettering, trademark, orother marking and becomes the outside.

When a blank of such material is formed into a cuplike shell, a smallamount of plastic coating is stripped and appears as "hairs or whiskersin the finished parts and these must be removed before succeedingoperations.

If the opposing force applied to the pressure pad is removed atprecisely a predetermined point during the forming of the shells, thehairs, whiskers or shreds are eliminated.

The apparatuses of the prior art have generally proved unsatisfactoryfor various reasons in releasing the pressure in the pressure pad at apredetermined point in the forming of the shell.

In the stamping apparatus disclosed herein, an expansion chamber isconnected by passageways to the hydraulic cushion. A hydraulic fluidsupply connected to the hydraulic cushion provides a yieldable opposinghydraulic force to a movement of the pressure pad. These passagewaysremain substantially constant in volume when hydraulic pressure isapplied to or removed from the hydraulic cushion to allow the hydraulicpressure in the hydraulic cushion to release without a response lag.After movement of the die for forming the workpiece through apredetermined distance, the expansion chamber is expanded with thecontinued movement of the die in its work stroke at a rate sufficient torelease the hydraulic pressure in the hydraulic cushion. Thus, theyieldable opposition of the pressure pad to the direction of movement ofthe upper die portion during shaping of the sheet material is removedsuch that the sheet material blank is properly formed thereby.

In some phases of the stamping industry, two or more shells are requiredto be formed simultaneously during each press stroke. The size of thedies required toform various shapes also necessarily change andtherefore, the center distance between the dies must also change. Sincethis center distance must be variable, the center distance between thecorresponding hydraulic cushions for each die must change acorresponding distance.

The stamping apparatus of the present invention provides for changingthe center distance between these corresponding hydraulic cushionswithout disconnecting the hydraulic system which reduces the timerequired to make a die change. In addition, the interconnectingpassageways between the hydraulic cushion and the fluid pressure supplyand expansion chamber are provided in rigid bodies to obtain asubstantially instantaneous hydraulic pressure release.

Accordingly it is anobject of this invention to provide a new andimproved apparatus in which a blank is held against a die during aforming operation by a pressure pad urged towardthe die by means of ahydraulic cushioning means which yieldably opposes movement of the die,the apparatus being such that the hydraulic pressure in the cushioningmeans can be relieved after a portion of the work stroke has beencompleted with a minimum of time lag so that the pressure pad whilemoving with the die will no longer apply a significant holding force tothe workpiece.

Another object of the present invention is to provide a new and improvedmethod and apparatus for releasing pressure in hydraulic cushioningmeans of a forming apparatus as the ram of the apparatus is movingthrough its work stroke and is dis placing pressure fluid from thecushioning means, in which apparatus and method a chamber in fluidcommunication with the cushioning means is expanded to receive fluiddisplaced from the cushioning means and to release the pressure thereinand preferably to establish a negative pressure in the cushioning means.

It is yet another object of this invention to provide a stampingapparatus having an expansion chamber connected to a hydraulic cushionand adapted to be mechanically expanded after a die is moved through apredetermined distance to remove the fluid pressure in the hydrauliccushion such that the pressure pad no longer yieldably opposes movement.

It is yet another object of this invention to connect a hydrauliccushion to an expansion chamber and a fluid pressure supply bysubstantially rigid bodies having passageways therein to allow hydraulicfluid to flow therebetween to accommodate for substantiallyinstantaneous pressure release of the fluid pressure in the hydrauliccushion.

It is yet another object of the present invention to provide a hydrauliccushion having a plunger mounted in a fluid cushion body having plasticmaterial interposed therebetween to decrease friction and the tendencyfor scratches to occur between the hydraulic cushion body and theplunger.

Yet another object of the invention is the provision of a hydrauliccushion adapted to provide individual yieldable opposing forces to aplurality of pressure pads such that each yieldable opposing force isremoved from its corresponding individual predetermined distance ofmovement of the upper die portion.

It is yet another object of the present invention to provide a stampingapparatus having a plurality of hydraulic cushions wherein the distancebetween the hydraulic cushions are adjustable while remaining inconstant communication with a hydraulic fluid supply and expansionchamber by a solid member having a passageway therein.

Still further objects, advantages and features of the present inventionwill be apparent to those skilled in the art to which it relates fromthe following detailed description made with reference to theaccompanying drawings; forming a part of the specification and in which:

FIG. 1 is a fragmentary sectional view of a stamping press for forming asheet of material and schematically embodying the present invention;

FIG.. 2 is a fragmentary sectional view of the hydraulic cushion andpressure control device shown in FIG. 1;

FIG. 3 is a perspective view of a blank of sheet material to be formed;

FIG. 4 is a perspective view of the sheet of material shown in FIG. 3fonned into a shell;

FIG. Sis an exploded view of the forming portion of FIG. 1 showing therelative positions of the upper and lower die portions and sheetmaterial blank as they come in contact with each other'during the workstroke of the upper die portion;

FIG. 6 shows the relative positions of the parts shown in FIG. 5 afterinitial movement of the upper die portion and corresponding movement ofthe pressure pad to partially form the shell of FIG. 4;

FIG. 7 shows the relative positions of the parts shown in FIG. 5 at apredetermined distance where the-yieldable opposing force on thepressure pad is removed{ FIG. 8 shows the relative positions of theparts shown in FIG. upon completion of the work cycle of the upper dieportion showing a properly formed shell;

FIG. 9 shows two hydraulic cushions mounted on a base mounting platesuch that the distance between them may be varied;

FIG. 10 is a fragmentary sectional view taken along line 10-40 of FIG. 9showing a telescopic fluid connection which allows the hydrauliccushions of FIG. 9 to be movable relative to each other withoutdisconnecting the hydraulic cushions;

FIG. 11 is atop view of a hydraulic cushion having a plurality ofplungers for biasing two pressure pads;

FIG. 12 is a sectional view of FIG. 11 taken along line 12- 12 of FIG. 11 and showing the porting therein;

FIG. 13 is a fragmentary sectional view of yet another hydraulic cushionwhich is adapted to bias two pressure pads showing the passages therein;and

FIG. 14 is a perspective view of the base and baseplate of the fluidcushion shown in FIG. 13 in perspective.

The present invention is illustrated as embodied in a stamping apparatusfor forming a cuplike shell from a sheet of material. In forming theshell, sheet material is supported on a pressure pad which encircles alower die over which the material is to be drawn by a cooperating upperdie. A hydraulic cushion is provided to yieldably oppose movement of thepressure pad by the upper die portion during formation of the shell.This yieldable opposition of the pressure pad against the upper dieportion is created by hydraulic pressure in the hydraulic cushion forcontrolling the sheet material during its formation. But this opposingforce is preferably removed after partial formation of the shell if theshell is to be properly formed. An expansion chamber is provided incommunication with the hydraulic cushion and is expanded with themovement of the upper die when the pressure is to be released so as torelieve the pressure in the hydraulic cushion. To further facilitate theremoval of pressure in the hydraulic cushion, the hydraulic pressure ispreferably disconnected.

Referring to FIG. 1, a stamping press 10 is partially shown and has alower mounting plate 14 and a ram 12 which moves from an open positionwith respect to the lower mounting plate 14 through a work stroke andreturns to the open position to form sheet material 16. The sheetmaterial 16 is partially supported on a lower die portion 26 which isconnected to the lower mounting plate 14 of the stamping press 10 by thethreaded fasteners 19. The sheet material 16 is also supported by apressure pad 24 which is supported by the plungers 28 of a hydrauliccushion 30 mounted to the lower mounting plate 14. The sheet material 16may be supplied in a strip or sheet stock and sheared to a blank shape18 as shown in FIG. 3 by movement of the ram through its work stroke.

The blank 18 is sheared from the sheet material 16 by a shearing platemounted on the upper die generally indicated at 22, which is connectedto the ram 12 by threaded fasteners 19. As the ram 12 begins movementthrough its work stroke, the sheet is sheared into the blank form 18 asshown in FIG. 3 by the shearing plate 20. After the shearing of theblank form 18 is accomplished, the shearing plate 20 will slide on itsmounting pins 32 which are slidably received in the upper die 22.

At this point in the downward work stroke of the ram 12, the holddownpad 33 which is slidably supported on the upper die 22 andbiased awayfrom the first member 22 by a pair of springs 35, holds the sheetmaterial 16 against the lower die portion 26. Thus, the blank form 18 iscontrolled such that it will not move relative to either the upper die22 or the lower die 26.

At the position shown in FIG. 5, the holddown pad 33 is in contact withthe blank 18 and opposed by the lower die portion 26 which is also incontact with the blank 18. The upper die portion 34 is in contact withthe peripheral surface of the blank 18 and yieldably opposed from movingdownwardly by the pressure pad 24.

The yieldable opposition of the pressure pad 24 is applied by ahydraulic cushion 30 as a result of hydraulic fluid supplied underpressure to the hydraulic cushion chambers 37 of the respective plungers28, as shown by FIG. 2. The hydraulic fluid pressure acts on the lowerends 28a of the plungers 28 to provide a yieldably opposing upward forcewhich may be I overcome by a sufficient downward force on the plungers28. Thus, as long as hydraulic pressure exists in the hydraulic cushionchambers 37, a yieldable opposing force exists but when the pressure isremoved, the force is also removed. The hydraulic fluid under pressureis supplied to the cushion chambers 37 by means of a passageway,generally noted 38, in the base plate 40 to which the hydraulic cushionis mounted. The number of plungers 28 provided by the hydraulic cushion30 may vary depending on the die design required to form the specifiedshell. Each of the plungers 28 of the improved construction are mountedin respective apertures 29 of hydraulic cushion body 25. Plastic sleeves31 are inserted in each aperture 29 and receive their respectiveplungers 28 therein. The plungers 28 are hardened, polished and coatedwith a low friction compound such as polytetrafluoroethylene resin. Thisimproved construction allows the plungers 28 to move with respect to thehydraulic cushion body 25 with a minimum of frictional resistance. Inaddition, the tendency for scratches to occur'on the plungers 28 issubstantially reduced.

Pressure control device 41 is also mounted on the base plate 40 and hasa passageway 39 in communication with the passageway 38 of the baseplate 40 such that the hydraulic pressure may be supplied from thehydraulic pressure supply 52 to the hydraulic cushion chambers 37. Anaperture 44 is provided in the body of the pressure control device 41and adapted to receive the floating piston 46 having an opening 48therein which defines a portion of the passage 39 through whichhydraulic fluid may be supplied to the hydraulic cushion chambers 37.The baseplate 40 has a hydraulic pressure passageway 50in communicationwith the passageway 39 such that hydraulic pressure may be supplied fromthe hydraulic pressure supply 52. Thus, the fluid pressure passageway54, including passageways 50, 39, and 38, connects the cushion chambers37 with the hydraulic pressure supply 52.

The hydraulic pressure supply 52 may include any conventional means ofsupplying pressurized fluid to conduit 56. The hydraulic pressure supply52 as shown further includes an accumulator 58 to maintain asubstantially constant pressure in the hydraulic fluid pressure supply52. Thus, pressure surges and fluctuations in the hydraulic pressuresupplied by the hydraulic pressure supply 52 are minimized to providefor consistent operation of the stamping apparatus of the immediateinvention. It should be understood that the accumulator 58 may be of anyconventional construction known to those skilled in the art and isprovided to maintain a more constant pressure relationship of the fluidpressure supply 52.

As the ram 12 continues to descend through its work stroke, the upperdie portion 34 begins to shape the-blank 18 as best shown in FIG. 6.During this downward movement, the pressure pad 24 moves downward withthe upper die portion 34, but is maintained in yieldable opposition tomovement of the upper die 22 by the hydraulic pressure. In this manner,the peripheral material of the blank 18 is held in compression between.the upper die portion 34 and the pressure pad 24 and controlled duringformation of the shell 21.

As the pressure pad 24 descends with the upper die portion 34, theplungers 28 move downwardin their complementary cushion chambers 37 suchthat the volume of the cushion chambers 37 is decreased. Throughout thismovement though, the pressure supplied to the cushion chamber 37 by thehydraulic pressure supply 52 remains constant such that the yieldableopposing force created by the hydraulic cushion 30 remains constant.

This constant yieldable opposing force by the pressure pad 24 againstthe upper die portion 34 continues to exist until a predetermineddistance 70, as shown in FIG. 7, is reached. After movement of the ram12 through the predetermined distance 70 of its work stroke, theyieldable opposing force is removed. A member 72 is attached to the ram12 and has a contact member connected thereto such as a threadedfastener 74. The predetermined distance'70 is determined by the positionof the threaded fastener 74 with respect to the extending rod 78 of thepressure control device. It should be understood that the contact member74 may be adjusted such that the predetermined distance 70 at which theyieldably opposing force is removed may be varied.

Thus, as the ram 12 moves through its work stroke, the contact member 74will contact the extending rod 78 and force the extending rod 78 into aposition such that the piston 82 attached to the extending rod 78 willblock the aperture 48 of floating piston 46 such that the hydraulicpressure from the hydraulic pressure supply 52 is effectivelydisconnected from the cushion chambers 37 of the hydraulic cushion 30.The extending rod 78 is received in an aperture 84 in the pressurecontrol device 41 with suitable bearing 88 interposed therebetween. Aseal 85 is provided such that the hydraulic fluid under pressure cannotescape therefrom. The piston 82, integral with the extending rod 78, isslidably received in the aperture 44 of the valve body 42 and hassuitable bearing member 90 and sealing means 91 interposed therebetween.

An expansion chamber 94 is provided by an opening 96 in the valve body42. The piston 82 includes a movable wall portion or shoulder 83 whichdefines a portion of the expansion chamber 94 and is adapted to expandthe expansion chamber 94 as the extending rod 78 and piston 82 move inresponse to the downward movement of the ram 12 through its work stroke.The expansion chamber 94 is connected to the cushion chamber 37 bypassageway 95 which includes passageway 38 in the baseplate 40. As thepiston 82 is moved, movable wall portion 83 of the expansion chamber 94moves correspondingly such that the expansion chamber 94 expands toinclude a portion of the body 42 defined by aperture 44. When thepredetermined distance 70 of the upper die portion 34 is traveled by theram 12, the contact surface 100 of piston 82 contacts the contactsurface 102 of floating piston 46 to block the passage 54 connecting thehydraulic pressure supply 52 to the cushion chambers 37 such that thehydraulic pressure supply 52 is disconnected from the hydraulic cushionchambers 37.

A spring 106 provides an initial bias for holding the floating piston 46in its upper position as shown in FIG. 2. In such a position theretaining member 109 engages a counterbored surface of the aperture 44to prohibit further upward movement of the floating piston 46. Asuitable hydraulic pressure sealing means 107 and bearing member 108 isprovided between the floating piston 46 and the aperture 44 to allowfree movement of the floating piston 46 in the aperture 44 whileprohibiting hydraulic fluid from the hydraulic fluid supply to passaround the floating piston 46. Thus, hydraulic fluid from the hydraulicfluid supply is required to flow through the aperture 44 of the floatingpiston 46 in order to create a pressure in the hydraulic cushionchambers 37 In order to better complete formation of the shell 21 asshown in FIG. 4 from the blank 18 as shown in FIG. 8, the yieldableopposing force of the pressure pad 24 must be removed at thepredetermined distance 70 of the work stroke of the ram 12, as shown inFIG. 7. Thus, when the upper die portion 34 completes the formation ofthe blank 18, as shown in FIG. 8, a smooth shell will be formed havingperipheral walls 18b which are substantially free of wrinkles, tears andsignificant changes in the wall section.

As the upper die portion 34 moves from the predetermined distance 70 tocomplete its work stroke, the pressure pad 24 continues to move in thesame direction as the upper die portion 34, but no longer provides ayieldable opposing force. Consequently, the plungers 28 continue to movein the same direction and continue to displace fluid in the hydrauliccushion chambers 37 The piston 82 and the floating piston 46 move acorresponding distance in response to the contact member 74. As thepiston 82 so moves, the rate of expansion of the expansion chamber 94 isgreater than the volume of hydraulic fluid displaced by the plungers 28in hydraulic cushion chambers 37. Since the expansion chamber 94 is incommunication with the hydraulic cushion chambers 37 through passageway95, the hydraulic pressure in the hydraulic cushion chambers 37 willcontinue to be relieved by such expansion. Thus, the yieldable opposingforce created on the plungers 28 by hydraulic fluid pressure thereon isremoved through the remainder of the work stroke of the ram 12.

It should be understood that the rate of expansion of the expansionchamber 94 may be equal to the rate of contraction of the hydrauliccushion cylinders 37 if the initial pressure created by the hydraulicpressure supply 52 before it is disconnected from the hydraulic cushion30 is removed. On the other hand, if the rate of expansion is greaterthan the rate of contraction of the hydraulic cushion chambers 37, thehydraulic fluid contained in the hydraulic cushion chambers 37 will besucked" out of the hydraulic cushion chambers 37. Thus, a vacuum will becreated on the plungers 28 and tend to pull the plungers 28 in thedirection of movement of the upper die portion 34 when shaping the blank18. I

But it should be apparent to those skilled in the art that the hydraulicpressure supply 52 need not be completely disconnected from thehydraulic cushion 30 in order to release the hydraulic fluid pressure inthe cushion cylinder if the expansion chamber 94 expands at any ratesufiicient to remove such pressure.

Once the blank 18 is formed into a shell 21, as shown in FIG. 4, the ram12 will move in an upward direction to return to its original position.As the ram 12 so moves, the contact member 74 allows the extending rod78 to return to its original position. This return movement isaccomplished by the hydraulic pressure from the hydraulic fluid pressuresupply 52 through the aperture 48 of passageway 39 creating an upwardforce on the piston 82. As the piston 82 returns to its originalposition, the spring 106 urges floating piston 46 to return to itsoriginal position. When the floating piston 46 has reached its originalposition, a retaining member 109 prohibits further upward movement ofthe floating piston 46.

The piston 82 continues to move in an upward direction due to thehydraulic pressure created by the hydraulic fluid supply 52. Throughoutthe upward movement of the piston 82, the expansion chamber 94 returnsto its original volume. The hydraulic fluid is supplied to the hydrauliccushion chambers 37 under pressure and returns the plungers 28 to theiroriginal position by creating an upward force on the'lower ends 280 ofthe plungers 28. When the piston 82 returns to its original position,hydraulic pressure is supplied by the hydraulic pressure supply meansthrough the hydraulic pressure passageway 54 to the hydraulic cushionchambers 37 to continue upward movement of the plungers 28 until theplungers 28, and consequently the pressure pad 24, return to theirrespective original positions.

It should be understood that as the pressure pad 24 returns to itsoriginal position, it may act as a stripper to remove the shell 21formed by the-blank 18 from the lower die 26. After ejection of theshell, the sheet material 16 may be advanced and the operationalsequence aforementioned continued repeatedly.

It should be noted that both the hydraulic pressure passageway 54 andthe passageway are each of a sufficient size to allow free flow ofhydraulic fluid and are defined by rigid bodies such that when hydraulicpressure is exerted, they do not enlarge or expand. This provides for amore instantaneous pressure release on the hydraulic cushion 30 bydecreasing the time lag associated with the contraction of the hydraulicpressure passageway 54 and the passageway 95 when hydraulic pressure isremoved since their normal contraction during this change in pressurewould act as an accumulator in the system.

It should be understood that any fluid such as a gas could be used insuch a hydraulic system hereinabove described. The

pressure control apparatus of the immediate invention could be utilizedto reduce the pressure in such a fluid system in response to movement ofthe ram through a predetermined portion of its work stroke as describedabove.

In order to facilitate charging of the hydraulic cushion chambers 37, athreadedplug 116 engages an extension 118 of passageway 38 and mayberemoved when hydraulic fluid is supplied by the hydraulic pressuresupply 52 t charge the system. When the plungers 28 are in the downposition such that they fill the hydraulic cushion chambers 37,hydraulic fluid may be supplied to. the assembly to substantially fillit. When the system is full, the threaded plug 116 is threadedly engagedwith passageway extension 118 to seal the system from leakagetherethrough.

Thus, it may be seen that a stamping apparatus which allows a blank 18to be shaped into a shell 21 having a wall portion 18a which issubstantially. free from wrinkles, tears, and rough edges is provided.ln order to accomplish this result, the present invention provides astamping apparatus wherein a pressure pad 24 supports the peripheralarea of a blank 18 and an upper die portion 34 is provided for shapingthe blank 18. A hydraulic cushion 30 contacts the pressure pad 24 toprovide a yieldable opposing force to the movement of the upper dieportion 34 as it shapes the material through the predetermined distance70. The yieldable opposing force is created by hydraulic pressure from ahydraulic pressure supply 52 acting on the lower ends 28a of theplungers 38 in the hydraulic cushion 30. After the upper die portion 34has moved through the predetermined distance 70, an expansion chamber 94which is connected by passageway 95 to the hydraulic cushion 30 expandsto remove the yieldable opposing force on the pressure pad 24 during theremainder of the work stroke of the upper die portion 34 such that ashell 21 is provided without detrimental wrinkling, cross-sectionalchanges or rough edges.

When two shells are required to be formed during one work stroke of thepress, a pair of upper and lower dies will be required to be mounted inthe stamping press. Consequently, a corresponding pair of hydrauliccushions will be required to provide their corresponding pressure padswith a force which yieldably opposes movement of the upper dies during aportion of the work stroke of the upper dies. It should be understoodthat the operation of each of these upper and lower die portions willoperate in the same manner as described hereinabove in connection withFIGS; 18. Since the shapes may be changed, the size of the dies andconsequently their center distances may change.

For ease of description, the suffixes a and b will be-used in connectionwith the common numerals of those shown in FIGS. l-8.

To change, the positions of the hydraulic cushion cylinders 30a and 30b,as best shown in FIG. 9, with respect to each other while maintainingthem in a centered relationship with respect to their correspondingpressure pads, a cushion base mounting plate 150 is attached to thelower mounting plate 14a of a stamping press. The base mounting plate150 has a slot- 152 to receive an extension 154 of a center spacer blockWhen locating the hydraulic cushion cylinders 30a and 30b with respectto their corresponding lower die portions, the spacer block 156 ispositioned such that its extension 154 is received by the slot 152. Theground surfaces 160 and 162 are provided on the spacer block 156 suchthat when the hydraulic cushion chambers 30a and 30b are incommunication with these surfaces 160 and 162, respectively, they willbe centered with respect to their corresponding lower and upper dieportions and corresponding pressure pad. Thus, the distance between thesurfaces 160 and 162 determines the center distance of the hydrauliccushions 30a and 301; when so positioned. it will be understood thatvarious spacer blocks 156 may be'used having different distances betweensurfaces 160 and 162 to provide for correspondingly different centers ofthe hydraulic cushion cylinders 30a and 30b when the dies are changed toprovide for manufacture of a different shell.

mounted on the base mounting plate 150 in a direction 165.

and 166, respectively since the ears 166 of baseplates 40a and 40b areretained by rails 170. The rails 170 are attached to the base mountingplate 150 by means of threaded fasteners 172.

' When the threaded fasteners 172 are loosened, the hydraulic cushions30a and 30b may be moved along the line of direction 165 to positionthem against surfaces and 162 of the spacer block 156. In this manner,the hydraulic cushions 30a and 30b may be properly centered with respectto their respective die portions. When the hydraulic cushions 30a and30b are properly positioned, the threaded fasteners 172 are tightenedsuch that they are retained on the base mounting plate 150.

The construction shown in FIGS. 9 and 10 includes novel fluidconnections between the hydraulic cushions 30a and 30b and the basemounting plate 150. When the hydraulic cushions 30a and 30b are slidalong direction while retained by the rails 170, the fluid connections176 and 176" do not require that the hydraulic system be disconnected toeffect such movement. For ease of description, only the hydraulicconnection 176 will be described in detail as shown in FIG. 10, but itshould be understood that the fluid connection 176' has correspondingparts and operates in a manner similar to the fluid connection 176.

Fluid connection 176 includes a tube 180 of solid material which issuitably attached to the baseplate 40a of hydraulic cushion 30a. Athreaded aperture 182 is provided in baseplate 40a to threadedly engagea threaded end portion 184 of the tube 180 to effect a fluidtight sealtherewith. Thus, the passageway 181 of the tube 180 is in communicationwith the passageway 38a in the baseplate 40a. 7

The tube 180 is telescopically received in an aperture 186 of theinterconnecting block 190. The interconnecting block 190 is attached tothe base mounting plate 150 and provides for an interconnection betweena passageway 192 in the base mounting plate 150 and a passageway 181 ofthe tube 180. Suitable sealing means 194 are provided between the tube180 and the aperture 186 to prohibit leakage of hydraulic fluid underpressure.

Hydraulic pressure may be supplied by the hydraulic pressure supply 52awhich is of a construction similar to the hydraulic pressure supply 52.The hydraulic pressure is supplied to a pressure control device 410which operates in a manner as described hereinabove in connection withthe pressure control device 41. It must be understood, though, that thevolume of the expanding chamber 94a of the pressure control device 41ais sufficient to release the pressure in both hydraulic cushions 30a and30b. It should also be apparent that a number of pressure controldevices similar to the construction as described in connection withpressure control device 41 may be used in a similar manner to releasethe yieldably opposing force on the pressure pad.

The passageways 95a and 39a extending from the pressure control device41a flow to a common passageway 191 which includes passageway 192 in theblock 190, the passageway 181, and the passageway 192 in the block 190'.Thus, the common passageway 191 may apply pressure to or remove pressurefrom the hydraulic cushions 30a and 30b. The operational cycle of thisdevice is similar to that above described in connection with thehydraulic cushion 30 and valve 41.

It should be pointed out that the hydraulic cushion cylinders 30a and30b may be moved respectively with each other such that their centersare adjusted without disconnecting their connections to the hydraulicsystem above described. These connections include passageways defined bysolid members throughout which allows for an instantaneous pressurerelease on the hydraulic cushions 30a and 30b by the valve 41. The

response time of this system is minimized since the members defining thehydraulic passageway 191 will not expand when hydraulic pressure isapplied thereto or contract when the fluid pressure is removedtherefrom.

When it is desirous for a blank to be formed in a shape having twosidewalls, it is necessary to have two pressure pads. The upper die 201,shown schematically in FIG. 13 and constructed in a manner known bythose skilled in the art, urges the blank 18 against the lower die 203and subsequently forms the blank 18 as shown in FIG. 13.

As the upper die 201 descends, a sidewall 200 is formed. At a firstpredetermined distance the first pressure pad 224 is relieved of itsyieldable opposing force to the downward movement of the upper die 224for reasons hereinabove set forth in connection with FIGS. 1-8.

This yieldable opposing force on the pressure pad 224 is created by theplungers 202 of the hydraulic cushion means 204. These plungers 202 arereceived in the apertures 206 as described in connection with theplungers 28 mounted in the hydraulic cushion 30. Hydraulic fluid underpressure in the chambers 210 of the hydraulic cushion 204 creates theyieldably opposing force on the plungers 202. The hydraulic pressure issupplied to the chambers 210 by a passageway 212 through a pressurecontrol device similar in construction to the pressure control device 41which is adapted to release pressure after the sidewall 200 has beenpartially formed and operates in a manner in conjunction with theplungers 202 similar to the operation of the apparatus shown in FIG. 2.Thus, the first pressure control device removes the yieldable opposingforce on the first pressure pad 230 in response to movement of the upperdie portion 201 through a first predetermined distance.

It should be understood that the passageway 212 connecting the firstchambers 210 of the hydraulic cushion 204 to the hydraulic pressuresupply includes a number of passageways 216 corresponding to each ofchambers 210 in base 218, as shown in perspective in FIG. 14. Thesepassageways 216 are in communication with a first annular groove 220 inthe base block 222. The first annular groove 220 is connect to apressure control device having a construction similar to that as shownby the pressure control device 41 as is apparent from the above.

After the yieldable opposing force on the pressure pad 224 has beenremoved, the sidewall 200 will continue to be formed until the pressurepad 224 bottoms out against surface 230 of lower die 203. At this point,the pressure pad 224 remains fixed with respect to the lower die 203 andthe upper die 201 continues to descend and deform the blank 18 such thata second sidewall 234 is formed.

Throughout a portion of the downward movement of the upper die 201 thepressure pad 241 yieldably opposes the downward movement of the upperdie 201 such that the blank is controlled.

The pressure pad 241 is supported by the plungers 240 which are receivedin apertures 242 of hydraulic cushion 204 and of a similar constructionto that mentioned in connection with the hydraulic cushion 30. Hydrauliccushion chambers 244 'are provided to receive hydraulic fluid underpressure and create a yieldable opposing force on the plungers 240 whichin turn transfer the force to the pressure pad 241. The hydraulic fluidis supplied through a passageway 246 which includes a passageway 250 inthe base plate 218 which is connected to a second annular groove 252 inthe base block 22, as best shown in perspective in FIG. 14. This annulargroove 252 is con nected to a second pressure control device constructedin accordance with the pressure control device 41 hereinabove describedwith a suitable hydraulic pressure supply associated therewith. Aftermovement of the upper die 201 through a second predetermined distance asindicated at 235 in FIG. 13, it is desirable to remove the yieldableopposing force created by the fluid pressure in the hydraulic cushionchambers 244. Thus, the second pressure controldevice constructed inaccordance with pressure control device 41 hereinabove describedreleases the pressure in the hydraulic cushion chambers 244 throughpassageway 246 in response to the downward movement of the upper die 201through a second predetermined distance 202. This allows for completeformation of a shell having sidewalls 200 and 234 with a minimum numberof wrinkled, cracked, or burred edges.

An alternative design for the passageways for a hydraulic cushion toform a shell having two sidewalls is shown in FIGS. 11 and 12. For easeof description, parts shown in FIGS. 11 and 12 which are common to partsshown in FIGS. 13 and 14 will be denoted by primed numerals. Thus, theplungers 202 and 240' operate in a similar manner as described inconnection with plungers 202 and 240 correspondingly.

The passageway 212' included a peripheral annular groove 260 extendingabout the periphery of the hydraulic cushion body 262 of the valve 256such that it is in communication with each of the three fluid chambers210' through corresponding passageways 264. The passageway 212' furtherincludes an outlet 273 which is in turn connected to a first valveconstructed in accordance with the valve 41 as described hereinabove andadapted to be actuated as hereinabove described in connection withhydraulic chambers 210.

A second annular groove 270 is included in passageway 246'. Thehydraulic cushion chambers 244' are in communication with the annulargroove 270 by means of passageways 272 connecting them therebetween. Thepassageway 246' further includes an outlet 274 which is in turnconnected to a second valve constructed in accordance with the valve 41as hereinabove described in connection with hydraulic chambers 244.

It should be understood that the hydraulic cushions representativelyshown in FIGS. 11-14 could also be advantageously used wherever it isdesirable to have a pressure pad with rings which apply differentpressure.

From the foregoing, it should be apparent that a stamping apparatus hasbeen provided with a pressure pad 24 for supporting sheet material 16thereon and a movable upper die 22 having a movable upper die portion 34for shaping the sheet material 16 supported on the pressure pad 24. Ahydraulic cushion 30 provides a yieldable opposing force on the pressurepad 24 to movement of the upper die portion 34 during shaping of thesheet material 16. This yieldable opposing force is created by means ofhydraulic pressure supplied to the hydraulic cushion 30. An expansionchamber 96 is connected to the hydraulic cushion 30 by passageway and isexpandable after movement of the upper die portion 34 through apredetermined distance 70 at a rate sufiicient to relieve the hydraulicpressure in the hydraulic cushion 30. Thus, after the 7 upper dieportion 34 has moved through the predetermined distance 70, theyieldable opposition by the hydraulic cushion 30 to movement of thepressure pad 24 in the direction of movement of the upper die portion 34during shaping of the sheet material 16 is removed.

Having described my invention, I claim:

1. In a machine, a first member movable in one direction along a path,hydraulic cushion means adapted to provide a yieldable opposing force tosaid member during a portion of its movement along said path, ahydraulic pressure supply for supplying hydraulic pressure to saidhydraulic cushion means for creating the yieldable opposing force,expansion chamber means defining an expansion chamber connected in fluidcommunication with said hydraulic cushion means, and actuating means forexpanding said chamber to completely remove the hydraulic pressure fromsaid hydraulic cushion means after said first member has moved through apredetermined portion of said path, said actuating means including meansfor expanding said chamber at a rate sufficient to reduce the hydraulicpressure in said hydraulic cushion means to a pressure which is equal toor less than ambient pressure.

2. In a machine having pressure pad means for supporting material and afirst member for shaping the material supported on said pressure padmeans, hydrauliccushion means yieldably opposing movement of saidpressure pad means in the one direction by hydraulic pressure from ahydraulic pressure supply, said first member upon movement effectingmovement of said pressure pad means during shaping of the material, andpressure control means for instantaneously and completely relieving theyieldably opposition of said hydraulic cushion means, said pressurecontrol means including expansion chamber means connected by passagewaysto said hydraulic cushion means and, expandable after said first membermoves through a predetermined portion of the work stroke to provide anincrease in volume greater than the volume of fluid'displaced by saidhydraulic cushion means during movement of said pressure pad means suchthat the yieldable opposition by said hydraulic cushion means iscompletely relieved.

3. A method for forming material partially supported by pressure padmeans with a movable upper die portion for forming the materialcomprising providing hydraulic pressure from a hydraulic pressure supplyto hydraulic cushion means through a pressure passage for yieldablyopposing motion of said pressure pad means in adirection opposite thedirection of movement of the upper die portion when the material isformed, and after movement of said pressure pad through a predeterminedportion of the work stroke expanding the volume of an expansion chamberconnected to said hydraulic cushion means at a volumetric rate which isgreater than the volumetric rate of displacement of hydraulic fluid fromsaid hydraulic cushion means such that the yieldable opposition tomovement of said pressure pad means is completely removed.

4. In a machine as defined in claim 1 wherein said hydraulic cushionmeans includes at least one cushion chamber adapted to receive hydraulicfluid under pressure, said one cushion chamber having a volume dependenton the position of said first member along said path, said expansionchamber means including a movable wall portion to vary the volume ofsaid expansion chamber, said one cushion chamber being connected to saidexpansion chamber by passageways therebetween, said expansion chamberbeing expanded at a rate greater than the rate of contraction of thevolume of said one cushion chamber on movement of said first memberthrough said predetermined portion of said path such that the yieldableopposition by said hydraulic cushion means is completely relieved andthe hydraulic pressure in said hydraulic cushion means is reduced to apressure which is below ambient pressure. i

5. In a machine as defined in claim 1 having means providing apassagewayconnecting said hydraulic pressure supply to said hydraulic cushionmeans, said. passageway being restricted after movement of said memberthrough said predetermined portion of said path.

6. In a machine as defined in claim 5 having a passageway connectingsaid hydraulic pressure supply to said hydraulic cushion means, andfurther comprising pressure control means for blocking said passagewayafter movement of said first member through said predetermined portionof said path to disconnect the hydraulic pressure supply from saidhydraulic cushion means. I

7. In a machine as defined in claim I wherein said expansion chamber isexpanded at a rate such that said hydraulic cushion means is urged inthe direction opposite to said one direction.

8. A machine, as defined in claim 4 wherein said passageways are definedby at least one substantially rigid body such that the volume of saidpassageways remains substantially constant upon removal of fluidpressure to allow a substantially instantaneous pressure release of thehydraulic pressure in said one hydraulic cushion means.

.9. In a machine as defined in claim 4 wherein a fluid chamber consistsof said one cushion chamber, passageways connecting said one cushionchamber to said expansion chamber, said fluid chamber having anincreasing volume after movement of said upper die portion through thepredetermined portion of said path such that the yieldable urging ofsaid pressure pad means in a direction opposite to the movement of saidupper die portion is completely removed at the predetermined distance.

10. In a machine as defined in claim 2 having a pressure passageway fromsaid hydraulic pressure supply to said hydraulic cushion means, saidpressure control means restricting said pressure passageway uponmovement of said first member through a predetermined portion of thework stroke.

11. In a machine as defined in claim 2 wherein said pressure controlmeans includes means to disconnect the hydraulic pressure supply fromsaid hydraulic cushion means upon movement of said movable die portionthrough the predetermined portion .of the work stroke.

12. In a machine as defined in claim 2 and including pressure controlmeans having means defining a pressure passageway therethroughconnecting the hydraulic pressure supply with said hydraulic cushionmeans and a piston movable .upon movement of said first member throughsaid predetermined portion of said work stroke to block the pressurepassageway in response to movement of said first member to disconnectsaid hydraulic pressure supply from said hydraulic cushion means.

13. In a machine as defined in claim 2 wherein said pressure controlmeans includes a piston, a floating piston, a pressure passagewayconnecting the hydraulic pressure supply with said hydraulic cushionmeans, a body having an aperture therein adapted to receive said pistonand said floating piston,

said floating piston defining a portion of said pressure passageway,said expansion chamber having a movable wall portion consisting of aportion of said piston, said piston operable from one position inresponse to movement of said first member through the predeterminedportion of the work stroke to block said pressure passageway andoperable to provide for the expansion of said expansion chamber from itsoriginal volume to receive the fluid displaced by said hydraulic cushionmeans.

14. In a machine as defined in claim 13 wherein said piston is adaptedto block said pressure passageway portion defined by said floatingpiston at a contact position in response to movement of said firstmember through the predetermined portion of the work stroke, said pistonand said floating piston remaining in contact throughout the remainderof the work stroke of said first member such that the hydraulic pressuresupply remains disconnected from said hydraulic cushion means throughthe remainder of the work stroke.

15. In a machine as defined in claim 14 wherein said pressure controlmeans includes biasing means to return said floating piston to saidcontact position during the upward stroke of 7 said first member.

l6. In a machine as defined in claim 13 wherein said piston is returnedto said one position by the hydraulic pressure from said hydraulicpressure supply during the upward stroke of said first member such thatthe volume of said expansion chamber returns to a volume less than saidoriginal volume such that said pressure passageway is no longer blockedby said piston.

17. In a machine as defined in claim 13 wherein said pressure pad nieansincludes a plurality of pressure pads, said hydraulic cushion meansincluding a corresponding plurality of hydraulic cushions, said pressurecontrol means including a corresponding plurality of pressure controldevices, each of said corresponding hydraulic cushions connected to oneof said corresponding pressure control devices and its correspondingpressure pad means.

18. In a machine as defined in claim 13 wherein said pressure pad meansincludes a first and a second part, said hydraulic cushion means havinghousing means including a base member having apertures therein,hydraulic plungers adapted to be slidably received by said apertures ofsaid housing means, at least one portion of said hydraulic plungershaving one end thereof in contact with said first part of said pressurepad means and at least another portion of said hydraulic plungers havingone end thereof in contact with said second part of said pressure padmeans, said housing means having a first and second annular groovetherein, said pressure control means including a first pressure controldevice connected to said first annular groove and a second pressurecontrol device connected to said second annular groove, said firstpressure control device adapted to actuate in response to movement ofsaid first member through a first predetermined portion of the workstroke and said second pressure control device adapted to actuate inresponse to movement of said upper die portion through a secondpredetermined portion of the work stroke.

19. In a machine as defined in claim 2 wherein said hydraulic cushionmeans includes plunger means, and a hydraulic cushion body having atleast one aperture therein adapted to receive said plunger means, saidplunger means adapted to have fluid pressure acting on one end portionthereof to provide for said yieldable opposition.

20. A method for forming material as defined in claim 3 which includesrestricting said pressure passage upon movement of said pressure padthrough a predetermined portion of its work stroke.

LII

1. In a machine, a first member movable in one direction along a path,hydraulic cushion means adapted to provide a yieldable opposing force tosaid member during a portion of its movement along said path, ahydraulic pressure supply for supplying hydraulic pressure to saidhydraulic cushion means for creating the yieldable opposing force,expansion chamber means defining an expansion chamber connected in fluidcommunication with said hydraulic cushion means, and actuating means forexpanding said chamber to completely remove the hydraulic pressure fromsaid hydraulic cushion means after said first member has moved through apredetermined portion of said path, said actuating means including meansfor expanding said chamber at a rate sufficient to reduce the hydraulicpressure in said hydraulic cushion means to a pressure which is equal toor less than ambient pressure.
 2. In a machine having pressure pad meansfor supporting material and a first member for shaping the materialsupported on said pressure pad means, hydraulic cushion means yieldablyopposing movement of said pressure pad means in the one direction byhydraulic pressure from a hydraulic pressure supply, said first memberupon movement effecting movement of said pressure pad means duringshaping of the material, and pressure control means for instantaneouslyand completely relieving the yieldably opposition of said hydrauliccushion means, said pressure control means including expansion chambermeans connected by passageways to said hydraulic cushion means andexpandable after said first member moves through a predetermined portionof the work stroke to provide an increase in volume greater than thevolume of fluid displaced by said hydraulic cushion means duringmovement of said pressure pad means such that the yieldable oppositionby said hydraulic cushion means is completely relieved.
 3. A method forforming material partially supported by pressure pad means with amovable upper die portion for forming the material comprising providinghydrauLic pressure from a hydraulic pressure supply to hydraulic cushionmeans through a pressure passage for yieldably opposing motion of saidpressure pad means in a direction opposite the direction of movement ofthe upper die portion when the material is formed, and after movement ofsaid pressure pad through a predetermined portion of the work strokeexpanding the volume of an expansion chamber connected to said hydrauliccushion means at a volumetric rate which is greater than the volumetricrate of displacement of hydraulic fluid from said hydraulic cushionmeans such that the yieldable opposition to movement of said pressurepad means is completely removed.
 4. In a machine as defined in claim 1wherein said hydraulic cushion means includes at least one cushionchamber adapted to receive hydraulic fluid under pressure, said onecushion chamber having a volume dependent on the position of said firstmember along said path, said expansion chamber means including a movablewall portion to vary the volume of said expansion chamber, said onecushion chamber being connected to said expansion chamber by passagewaystherebetween, said expansion chamber being expanded at a rate greaterthan the rate of contraction of the volume of said one cushion chamberon movement of said first member through said predetermined portion ofsaid path such that the yieldable opposition by said hydraulic cushionmeans is completely relieved and the hydraulic pressure in saidhydraulic cushion means is reduced to a pressure which is below ambientpressure.
 5. In a machine as defined in claim 1 having means providing apassageway connecting said hydraulic pressure supply to said hydrauliccushion means, said passageway being restricted after movement of saidmember through said predetermined portion of said path.
 6. In a machineas defined in claim 5 having a passageway connecting said hydraulicpressure supply to said hydraulic cushion means, and further comprisingpressure control means for blocking said passageway after movement ofsaid first member through said predetermined portion of said path todisconnect the hydraulic pressure supply from said hydraulic cushionmeans.
 7. In a machine as defined in claim 1 wherein said expansionchamber is expanded at a rate such that said hydraulic cushion means isurged in the direction opposite to said one direction.
 8. A machine asdefined in claim 4 wherein said passageways are defined by at least onesubstantially rigid body such that the volume of said passagewaysremains substantially constant upon removal of fluid pressure to allow asubstantially instantaneous pressure release of the hydraulic pressurein said one hydraulic cushion means.
 9. In a machine as defined in claim4 wherein a fluid chamber consists of said one cushion chamber,passageways connecting said one cushion chamber to said expansionchamber, said fluid chamber having an increasing volume after movementof said upper die portion through the predetermined portion of said pathsuch that the yieldable urging of said pressure pad means in a directionopposite to the movement of said upper die portion is completely removedat the predetermined distance.
 10. In a machine as defined in claim 2having a pressure passageway from said hydraulic pressure supply to saidhydraulic cushion means, said pressure control means restricting saidpressure passageway upon movement of said first member through apredetermined portion of the work stroke.
 11. In a machine as defined inclaim 2 wherein said pressure control means includes means to disconnectthe hydraulic pressure supply from said hydraulic cushion means uponmovement of said movable die portion through the predetermined portionof the work stroke.
 12. In a machine as defined in claim 2 and includingpressure control means having means defining a pressure passagewaytherethrough connecting the hydraulic pressure supply with saidhydraulic cushion means and a piston movable upon movement of said firstmember Through said predetermined portion of said work stroke to blockthe pressure passageway in response to movement of said first member todisconnect said hydraulic pressure supply from said hydraulic cushionmeans.
 13. In a machine as defined in claim 2 wherein said pressurecontrol means includes a piston, a floating piston, a pressurepassageway connecting the hydraulic pressure supply with said hydrauliccushion means, a body having an aperture therein adapted to receive saidpiston and said floating piston, said floating piston defining a portionof said pressure passageway, said expansion chamber having a movablewall portion consisting of a portion of said piston, said pistonoperable from one position in response to movement of said first memberthrough the predetermined portion of the work stroke to block saidpressure passageway and operable to provide for the expansion of saidexpansion chamber from its original volume to receive the fluiddisplaced by said hydraulic cushion means.
 14. In a machine as definedin claim 13 wherein said piston is adapted to block said pressurepassageway portion defined by said floating piston at a contact positionin response to movement of said first member through the predeterminedportion of the work stroke, said piston and said floating pistonremaining in contact throughout the remainder of the work stroke of saidfirst member such that the hydraulic pressure supply remainsdisconnected from said hydraulic cushion means through the remainder ofthe work stroke.
 15. In a machine as defined in claim 14 wherein saidpressure control means includes biasing means to return said floatingpiston to said contact position during the upward stroke of said firstmember.
 16. In a machine as defined in claim 13 wherein said piston isreturned to said one position by the hydraulic pressure from saidhydraulic pressure supply during the upward stroke of said first membersuch that the volume of said expansion chamber returns to a volume lessthan said original volume such that said pressure passageway is nolonger blocked by said piston.
 17. In a machine as defined in claim 13wherein said pressure pad means includes a plurality of pressure pads,said hydraulic cushion means including a corresponding plurality ofhydraulic cushions, said pressure control means including acorresponding plurality of pressure control devices, each of saidcorresponding hydraulic cushions connected to one of said correspondingpressure control devices and its corresponding pressure pad means. 18.In a machine as defined in claim 13 wherein said pressure pad meansincludes a first and a second part, said hydraulic cushion means havinghousing means including a base member having apertures therein,hydraulic plungers adapted to be slidably received by said apertures ofsaid housing means, at least one portion of said hydraulic plungershaving one end thereof in contact with said first part of said pressurepad means and at least another portion of said hydraulic plungers havingone end thereof in contact with said second part of said pressure padmeans, said housing means having a first and second annular groovetherein, said pressure control means including a first pressure controldevice connected to said first annular groove and a second pressurecontrol device connected to said second annular groove, said firstpressure control device adapted to actuate in response to movement ofsaid first member through a first predetermined portion of the workstroke and said second pressure control device adapted to actuate inresponse to movement of said upper die portion through a secondpredetermined portion of the work stroke.
 19. In a machine as defined inclaim 2 wherein said hydraulic cushion means includes plunger means, anda hydraulic cushion body having at least one aperture therein adapted toreceive said plunger means, said plunger means adapted to have fluidpressure acting on one end portion thereof to provide for said yieldableoppoSition.
 20. A method for forming material as defined in claim 3which includes restricting said pressure passage upon movement of saidpressure pad through a predetermined portion of its work stroke.
 21. Amethod for forming material as defined in claim 20 in which restrictingsaid pressure passage includes blocking said pressure passage such thatthe hydraulic pressure supply is disconnected from said hydrauliccushion means.
 22. A method for forming material as defined in claim 3in which expanding said expansion chamber includes expanding the volumeof said expansion chamber at a rate greater than the rate of volumedisplaced by said hydraulic cushion means such that the yieldableopposition to movement of said pressure pad means is completely removed.